(PureBasic) Verify JWT Using an ECC Public Key (ES256, ES384, ES512)

Demonstrates how to verify a JWT that was signed using an ECC private key.

This example verifies the ECC signature. It also does the following:

• Checks to see if the time constraints ("nbf" and "exp") are valid.
• Recovers the original JOSE header.
• Recovers the original claims JSON.

Chilkat PureBasic Module Download Chilkat PureBasic Module

IncludeFile "CkJwt.pb"
IncludeFile "CkJsonObject.pb"
IncludeFile "CkPublicKey.pb"

Procedure ChilkatExample()

    ; Demonstrates how to verify an JWT using an ECC public key.

    ; This example requires the Chilkat API to have been previously unlocked.
    ; See Global Unlock Sample for sample code.

    pubKey.i = CkPublicKey::ckCreate()
    If pubKey.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success.i = CkPublicKey::ckLoadFromFile(pubKey,"qa_data/pem/ecc_public.pem")

    jwt.i = CkJwt::ckCreate()
    If jwt.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    token.s = "eyJhbGciOiJFUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJodHRwOi8vZXhhbXBsZS5vcmciLCJzdWIiOiJKb2huIiwiYXVkIjoiaHR0cDovL2V4YW1wbGUuY29tIiwiaWF0IjoxNDg1NzA4NzkyLCJuYmYiOjE0ODU3MDg3OTIsImV4cCI6MTQ4NTcxMjM5Mn0.wqsuyJpxJ073ox-lOiLFqG1lQocXe4hGf2XGZJRrO3qn0UusxI_bu3Gzky8gBsH4sA4u9TWZn5M-1wYMMIJk6Q"

    ; First verify the signature.
    sigVerified.i = CkJwt::ckVerifyJwtPk(jwt,token,pubKey)
    Debug "verified: " + Str(sigVerified)

    ; Let's see if the time constraints, if any, are valid.
    ; The above JWT was created on the afternoon of 16-May-2016, with an expiration of 1 hour.
    ; If the current system time is before the "nbf" time, or after the "exp" time,
    ; then IsTimeValid will return false/0.
    ; Also, we'll allow a leeway of 60 seconds to account for any clock skew.
    ; Note: If the token has no "nbf" or "exp" claim fields, then IsTimeValid is always true.
    leeway.i = 60
    bTimeValid.i = CkJwt::ckIsTimeValid(jwt,token,leeway)
    Debug "time constraints valid: " + Str(bTimeValid)

    ; Now let's recover the original claims JSON (the payload).
    payload.s = CkJwt::ckGetPayload(jwt,token)
    ; The payload will likely be in compact form:
    Debug payload

    ; We can format for human viewing by loading it into Chilkat's JSON object
    ; and emit.
    json.i = CkJsonObject::ckCreate()
    If json.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkJsonObject::ckLoad(json,payload)
    CkJsonObject::setCkEmitCompact(json, 0)
    Debug CkJsonObject::ckEmit(json)

    ; We can recover the original JOSE header in the same way:
    joseHeader.s = CkJwt::ckGetHeader(jwt,token)
    ; The payload will likely be in compact form:
    Debug joseHeader

    ; We can format for human viewing by loading it into Chilkat's JSON object
    ; and emit.
    success = CkJsonObject::ckLoad(json,joseHeader)
    CkJsonObject::setCkEmitCompact(json, 0)
    Debug CkJsonObject::ckEmit(json)


    CkPublicKey::ckDispose(pubKey)
    CkJwt::ckDispose(jwt)
    CkJsonObject::ckDispose(json)


    ProcedureReturn
EndProcedure